This application claims priority to International Application No. PCT/DE00/01919 which was published in the German language on Jun. 9, 2000.
1. Technical Field of the Invention
The invention relates to the field of electrical components, and in particular, to components used in the design of vacuum interrupters, the housing of which has a tubular ceramic insulator and two end plates and in which the ceramic insulator is provided with an internally encircling step for securing a cylindrical vapor shield.
2. Background of the Invention
In order to protect ceramic insulators from deposits of electrode material which is vaporized during switching operations, it is customary to arrange the vapor shield at a floating potential. Typically, the insulated arrangement of the vapor shield is provided with the ceramic insulator with an internally encircling step, on one side of which the vapor shield bears by means of a conically tapering section, which merges into a cylindrical region. On the other side, there is a holding ring, which concentrically surrounds the cylindrical region of the vapor shield and is connected thereto in a positively-locking manner and with a material-to-material bond. This holding ring may have a cylindrical region and an axially adjoining, annularly bulging region, the cylindrical region being connected to the cylindrical region of the vapor shield and the annularly bulging region bearing against the step of the insulator (EP 0 309 978 A2, FIG. 5; U.S. Pat. No. 4,896,008).
It is also known to fix the vapor shield to an internally encircling step without a specific holding ring, as a result of the free end of the tapered region of the vapor shield being flanged on the other side of the step (EP 0 406 955 B1/U.S. Pat. No. 5,077,883 A).
Additionally, it is known to secure a continuously cylindrical shield to the step with the aid of a holding ring, the holding ring having an annular section, which is soldered or welded to the vapor shield, and holding parts which protrude radially on both sides of the step (U.S. Pat. No. 3,586,801 A).
To secure a vapor shield at a floating potential in vacuum interrupters whose housing has at least two hollow cylindrical ceramic insulators, it is also known to provide a metallic annular disk, which is arranged between the ceramic insulators, with a shoulder extending in the axial direction of the vacuum interrupter, in order to hold the vapor shield. This shoulder may be designed as a conically tapered piece of tube and may be provided by means of a layer of silver applied by electrodeposition, in order, when soldering the two ceramic insulators to the annular disk, at the same time to connect the vapor shield with a material-to-material bond to the vapor shield (DE 44 29 379 A1).
In one embodiment of the invention, there is a vacuum interrupter. The interrupter includes, for example, a housing which has a tubular ceramic insulator and two end plates, and in which the ceramic insulator is provided with an internally encircling step for securing a cylindrical vapor shield, the vapor shield bearing on one side of the step by means of a conically tapered section, which ends in a cylindrical region, and being fixed to the step by means of a holding ring which bears against the other side of the step, concentrically surrounds the vapor shield and is connected to the vapor shield in a positively-locking manner and with a material-to-material bond, wherein the holding ring has a cylindrical region, which is supported on the step of the ceramic insulator, and a collar which adjoins the cylindrical region, projects inward and is in the form of an arc of a circle, and the end of the cylindrical end region of the vapor shield is flanged onto the collar of the holding ring, without projecting axially beyond the holding ring.
In another aspect of the invention, the vapor shield and the holding ring consist of copper and are soldered by means of a copper/silver eutectic which has formed from an approximately 20 to 50 xcexcm thick silver coating on the holding ring.